The present invention relates to smoking articles such as cigarettes, and in particular to process for providing a flavorful and aromatic composition similar to those characteristics of certain tobaccos.
Popular smoking articles, such as cigarettes, have a substantially rod shaped structure and include a charge of smokable material such as strands or shreds of tobacco (e.g., cut filler) surrounded by a paper wrapper thereby providing a so-called xe2x80x9ctobacco rod.xe2x80x9d Numerous popular cigarettes have cylindrical filter elements aligned in an end-to-end relationship with the tobacco rod. Typically, filter elements are constructed from fibrous materials such as cellulose acetate, have a circumscribing plug wrap, and are attached to the tobacco rod using tipping material.
Many types of smoking products and improved smoking articles have been proposed through the years as improvements upon, or as alternatives to, the popular smoking articles. Recently, U.S. Pat. No. 4,708,151 to Shelar; U.S. Pat. No. 4,714,082 to Banerjee et al.; U.S. Pat. No. 4,756,318 to Clearman et al.; and U.S. Pat. No. 4,793,365 to Sensabaugh, Jr. et al.; and European Patent Publication Nos. 212,234 and 277,519 propose cigarettes and pipes which comprise a fuel element, an aerosol generating means physically separate from the fuel element, and a separate mouth-end piece. Such types of smoking articles provide natural tobacco flavors to the smoker thereof by heating, rather than burning, tobacco in various forms.
Flavor and aroma are important characteristics of smoking articles. To improve the flavor and aroma in smoking articles, flavorful and aromatic substances, including various natural extracts, have been included in smoking articles. For example, various processes for producing and using tobacco extracts, aroma oils and concentrates are proposed in the U.S. Pat. No. 3,136,321 to Davis; U.S. Pat. No. 3,316,919 to Green; U.S. Pat. No. 3,424,171 to Rooker; U.S. Pat. No. 4,421,126 to Gellatly and U.S. Pat. No. 4,506,682 to Mueller and European Patent Publication No. 338,831 to Clapp et al.
U.S. Pat. No. 5,413,122 to Shu issued on May 9, 1995 discloses making a flavorful and aromatic composition from xcex2-hydroxy xcex1-amino acids by contacting the amino acids with a liquid having an aqueous character followed by heat treatment in an enclosed environment to provide an aqueous solution of volatile pyrazine flavorants. The ratio of liquid to amino acid is 4:1 to 40:1. The resulting aqueous extract containing flavorful pyrazines is then applied to smoking materials to provide flavor and aroma in the smoking articles.
It has also been proposed to react sugars with amino acids to produce desirable flavorants for smoking articles and foods. For example, U.S. Pat. No. 3,478,015 discloses heating an amino acid and a sugar in the presence of a polyhydric alcohol and using the reaction product as a flavoring material.
U.S. Pat. No. 3,920,026 describes reacting the amino acid valine with a sugar, other hydroxycarbonyl compound, or dicarbonyl compound under heat treatment in a solvent such as glycerol or propylene glycol and at a temperature of about 100xc2x0 C. to about 200xc2x0 C. for about 0.5 to 5 hours. Optionally, a catalyst such as a flavanoid or hydroxyacid is included in the reaction. The reaction products can be used as flavorants in tobacco compositions.
U.S. Pat. No. 4,306,577 discloses the production of flavorants for smoking compositions by reacting reducing sugars and selected amino acids in the presence of ammonium hydroxide and optionally in the presence of an aldehyde in an essentially solvent-free system at a temperature range of 90xc2x0 C. to 115xc2x0 C. The selected amino acids are those that have at least two nitrogens such as glutamine, asparagine, lysine, and arginine.
Similarly, U.S. Pat. No. Re. 32,095 discloses reacting a reducing sugar with a source of ammonia in the presence of a trace amount of certain amino acids at a temperature in the range of about 90xc2x0 C. to about 115xc2x0 C. for about 5 to 15 minutes. The trace amino acids include aspartic acid, glutamic acid, asparagine, and glutamine. The weight ratio of sugar to amino acid is in the range of 200-300:1, and the weight ratio of sugar to ammonia source is about 5-15:1.
Because of the volatile nature of flavorant and aroma materials, they are often lost during use in cigarette manufacturing steps. Also quantities of the flavorant and aroma materials can diminish during the storage of the finished smoking articles and it is often necessary to increase the initial content of flavorants to compensate.
In accordance with the present invention, highly desirable flavorful and aromatic substances, and particularly flavorful and aromatic substances similar to and complementing those found in smokable materials are generated by heating a mixture comprising a reducing sugar source, a base catalyst, and an amino acid source material having a selectively enriched content of at least one amino acid selected from the group consisting of serine, threonine, valine, leucine, and isolecine. The resulting composition of flavorful and aromatic substances from the reaction includes a substantial quantity of flavorful and aromatic pyrazines that have low volatility and a low sensory threshold, i.e., powerful sensory attributes at very low concentrations. Examples of such pyrazines include, but are not limited to, methylcyclopentapyrazine, cyclopentapyrazine, 2-methyl-5,6,7,8-tetrahydroquinoxaline, dimethyl-isopropenyl pyrazine, dimethyl-propenyl pyrazine, methyl-propenyl pyrazine, acetylpyrazine, 2,3,5-trimethyl-6-ethylpyrazine, 2-methyl-3,5-dimethyl pyrazine, 2,6-diethyl pyrazine, trimethyl pyrazine, dimethyl pyrazine, etc. These pyrazines are characterized by larger side chains than flavorant pyrazines normally added to tobacco and/or generated in substantial quantities during smoking. The larger side chains have dual effects of decreasing the volatility of the flavorant while at the same time increasing the flavor potency of the flavorant substances typically by many orders of magnitude. Thus, less quantities of the flavorant and aroma materials can be used in smoking articles to provide a significantly greater enhancement of flavor and aroma. At the same time, loss of the flavorants during manufacturing and storage of the smoking articles is minimal.
Accordingly, in a first aspect, the present invention relates to a method for providing flavorful and aromatic substances for use in a smoking article. A mixture is provided comprising a reducing sugar source, a base catalyst, and an amino acid source having a selectively enriched content of at least one amino acid selected from the group consisting of serine, threonine, valine, leucine, and isoleucine. The mixture is then subjected to heat treatment for a time and under conditions sufficient to provide flavorful and aromatic substances.
The amino acid source can be a natural material containing endogenous free amino acids, or a composition comprising extracted or synthetic amino acids. The selective enrichment is the result of the incorporation of one or more exogenous free amino acids selected from the group consisting of serine, threonine, valine, leucine, and isoleucine in the amino acid source. Preferably, the mixture contains from about 0.1 to about 20%, more preferably from about 0.5% to about 10%, and most preferably from about 3% to about 5% by weight, e.g., 4% by weight, cumulatively, of amino acids selected from the group consisting of serine, threonine, valine, leucine, and isoleucine based on the total weight of the mixture.
Preferably, the mixture comprises materials normally used in casing, such as licorice and cocoa that contain endogenous free amino acids. More preferably, the mixture is formed by adding at least one desirable amino acid and at least one base catalyst to a conventional casing.
The mixture of reducing sugar source material, base catalyst and the amino acid source having a selectively enriched content of serine, threonine, leucine, and/or isoleucine is subjected to heat treatment at a temperature of at least about 175xc2x0 F. to provide a reaction material. Normally, the mixture is exposed to a temperature sufficiently high and for a period of time sufficiently long so as to provide a reaction material which exhibits a pleasant flavor and aroma. However, it is preferable that the reaction material is not exposed to such a high temperature for a sufficiently long period of time so as to provide a reaction material which exhibits a burnt, tarry, overly bitter or highly metallic flavor.
In a preferred embodiment, the mixture is subjected to heat treatment in an enclosed system under pressure. A pressure controlled environment is provided by a pressure chamber or vessel which provides, during heat treatment, containment of the components of the mixture such that the lighter active compounds formed (e.g., ammonia, acetaldehyde, carbonyls, etc.) are retained within the vessel or chamber and can react to generate the flavorful and aromatic substances. Heat treatment is preferably conducted at a typical pressure range of from about 10 psig to about 1,000 psig, normally from about 20 psig to about 500 psig.
The resulting flavorful and aromatic substances includes pyrazine and pyridine components, having relatively low volatility and potent flavors. The flavorful and aromatic substances are useful as casing or top dressing components for tobacco laminae and cut filler, as well as for other smokable materials. Alternatively, such flavorful and aromatic substances are useful in those types of smoking articles described in U.S. Pat. No. 4,708,151 to Shelar; U.S. Pat. No. 4,714,082 to Banerjee et al.; U.S. Pat. No. 4,756,318 to Clearman et al.; and U.S. Pat. No. 4,793,365 to Sensabaugh et al.; as well as European Patent Publication Nos. 212,234 and 277,519.
The flavorful and aromatic compositions also are useful as cigarette filter additives. For example, the flavorful and aromatic compositions can be incorporated into low-density polyethylene and formed into strands, and then incorporated into cigarette filters as described in U.S. Pat. No. 4,281,671 to Bynre et al. and U.S. Pat. No. 4,826,905 to Green, Jr. et al. The flavorful and aromatic compositions also are useful as cigarette wrapper additives; or as additives to the inner regions of cigarette packages (e.g., within a paper/foil laminate of cigarette package or within a low density polyethylene film which is placed within a cigarette package) in order to provide a desirable cigarette aroma and xe2x80x9cpack aroma.xe2x80x9d
Because the aromatic flavorants generated in the method of this invention have relatively low volatility, the loss of flavorants and aroma materials during the manufacturing process and storage of smoking articles is reduced. In addition, the aromatic flavorants have a dramatically high flavor potency, i.e., powerful sensory attributes at very low concentrations. As a result, smoking articles with improved flavor and aroma can be made with the aromatic flavorants. Further, the smoking articles can have more consistent and uniform flavorful and aromatic characters.
The foregoing and other advantages and features of the invention, and the manner in which the same are accomplished, will become more readily apparent upon consideration of the following detailed description of the invention taken in conjunction with the accompanying examples, which illustrate preferred and exemplary embodiments.